Table of Content

    16 February 2011
    Volume 41 Issue 1
    Study of pitch shifting technology and the sound quality evaluating
    ZHANG Xiao-rui, TIAN Lan*
    Abstract ( 509 )   PDF (1526KB) ( 3652 )   Save
    Related Articles | Metrics

    Three pitch shifting methods were studied and implemented,which were the improved synchronized overlap-add fixed synthesis(SOLA-FS) method, interpolation-on-frequency method, and the phase vocoder method. The improved SOLA-FS method was especially discussed in detail. Principles and characteristics were analyzed and simulation results were provided. In the experiments, it was found that the three methods could all achieve the effects of pitch-shifting, that is the pitch of the audio would be changed but the duration would be kept unchanged. But the auditory perceptions of the three methods were different. So, a sound quality evaluation test was carried out. The results of auditory evaluation tests showed that, under the given pitch-shifting ratio, whether for up or down, the sound quality processed by the improved SOLA-FS method is the best.

    Adaptive modulated cooperative communication based on relay selection and power allocation
    LI Rong-kai1,2, BAI Zhi-quan1
    Abstract ( 279 )   PDF (909KB) ( 1298 )   Save
    Related Articles | Metrics

    Cooperative communication technology can exploit spatial diversity to improve system performance. In the case that the channel state information is known at the source node, a larger power gain can be obtained. A new scheme of adaptive modulation for a cooperative system was presented. This scheme utilized spacetime coding, a power allocation algorithm and relay selection technique, which significantly improved the system throughput with a certain bit error rate requirement. The performance of the proposed scheme was compared with the other existing adaptive and non-adaptive schemes. The results showed that the proposed adaptive modulation scheme had superior average throughput performance and could stably satisfy the bit error rate constraint.

    Underwater object detection based on background subtraction and a saliency map
    WANG Xiu-fen, WANG Hui-yuan, WANG Song
    Abstract ( 311 )   PDF (1391KB) ( 1919 )   Save
    Related Articles | Metrics

    Detecting small low-contrast targets is a difficult hotspot, especially in underwater videos captured by moving remoteoperated vehicles. According to the features of seabed videos, a small-targets detection method based on background subtraction and a saliency map was proposed. The saliency map was used to improve the contrast of targets that were still not clear enough after background subtraction and to make them easier to be segmented from the background. Whether or not the targets appeared in the video was determined with the prior knowledge about the largest number of subjects in a singleframe to avoid wrong detection and improve the stability of the detection system. Experimental results showed that unclear objects could be better detected with the proposed method than with conventional background subtraction.

    Comparison of KPCA transformation matrices with definite and indefinite kernels for high-dimensional data
    CUI Yan, FAN Li-ya
    Abstract ( 358 )   PDF (778KB) ( 1973 )   Save
    Related Articles | Metrics

    The transformation matrices in the first stage of two-stage dimension reduction KPCA (kernel principal component analysis)+LDA (linear discriminant analysis) influenced the classification results of data. For linear non-separated problems, the influence of the transformation matrices in the first stage of KPCA+LDA to the classification results with definite kernels and then with indefinite kernels was first studied. In addition, experiments were provided for analyzing and illustrating the results.

    Robot navigation in a large scale environment based on distributed navigation information
    TIAN Guo-hui, ZHANG Tao-tao*, WU Hao, XUE Ying-hua, ZHOU Feng-yu
    Abstract ( 302 )   PDF (2517KB) ( 1610 )   Save
    Related Articles | Metrics

     A distributed navigation information acquisition mode (DNIAM) based on cognition theory was proposed for robot navigation in large scale semi-unknown environment. A new style of artificial landmark was designed adopting the two-dimensional bar code technology, and the methods to identify and read the artificial landmarks were simultaneously given. By placing relevant artificial landmarks on the critical positions, the robot navigation in the absolute large scale semi-unknown environment could  be divided into a global guide layer and a local search layer based on the distributed navigation information. The DNIAM makes robot navigation in large scale semi-unknown environment get rid of the restriction of the traditional mode of “map building-global locating-path planning”. The validity of this method was verified by experiments.

    Design and implement of the onboard computer software system of service robots for helping the aged and disabled
    ZHOU Feng-yu, TIAN Guo-hui, GUO Dan, ZHOU Xiang-zhang
    Abstract ( 353 )   PDF (1139KB) ( 1480 )   Save
    Related Articles | Metrics

    Aiming at the service robots for helping the aged and the disabled in the family and hospital environment, the architecture of the onboard computer software for service robots was designed based on behavior control. Then a hardware communication layer, protocol parsing layer, behavior layer and behavior decision layer of the software system were explained in detail. A variety of abstract objects was used to organize the code in software programming, and it was realized by the object-oriented C++ programming language. By using fuzzy control and the weighted synthesizing based multi-action fusion mechanism in the software, the service robot complex behavior control was better realized. Experimental and application results showed that the software system had many merits such as friendly interface, stable performance, convenient usage, good expansibility, and better meets the requirements of the service robots to software system on onboard computer in the home and medical environments. In reality, it has some potential benefits for their applications in relative fields.

    CC2431 based intelligent space locating system
    SONG Bao-ye, TIAN Guo-hui, ZHOU Feng-yu
    Abstract ( 271 )   PDF (1119KB) ( 1331 )   Save
    Related Articles | Metrics

    A Z-stack based intelligent space locating system was built on an existing wireless sensor networks platform in intelligent space with the support of CC2431. The working process was analyzed for all kinds of nodes, and the command cluster based operational mechanism of the locating system was described in detail. Information format was also illustrated for the command cluster of locating system. Experimental  results showed that this locating system could satisfy  the application requirements in intelligent space.

    Discrete variable control systems based on a discrete reaching law
    HUANG Bin
    Abstract ( 294 )   PDF (781KB) ( 1676 )   Save
    Related Articles | Metrics

    The problem of variable control for discrete-linear systems was discussed. A new discrete reaching law was presented   to deal with the flaw which exits in the conventional variable structure reaching law method. The sliding mode determined by this reaching law could be divided into two areas in the reaching process and the sliding mode trajectory could be converged to zero. The different reaching characteristics of the sliding mode trajectory were considered. The width of two areas might be changed by the adjustment of control parameters so that it enabled the sliding mode trajectory to pass through the switch surface as little as possible, thus the guarantee of control system chattering weakening and robustness was achieved. Good robustness of the discrete variable controller designed by this reaching law was proved. The simulation results  showed the superiority of this discrete reaching law method for nominal systems and good control performance for uncertain systems.

    Global disturbance rejection of a class of nonlinear systems with unknown external disturbances
    JIANG Yuan1,2, LIU Shu-tang1*
    Abstract ( 293 )   PDF (678KB) ( 1516 )   Save
    Related Articles | Metrics

    The global rejection problem for a class of nonlinear systems with unknown external disturbances was studied. The unknown external disturbances contain an unknown bounded disturbance and a class of nonharmonic periodic disturbance generated by a nonlinear exosystem. Based on the normalized parameter internal model, a new nonlinear internal model was designed by utilizing the state variable system and the external system structure. Based on the controller for the disturbancefree system, a state feedback controller was designed to ensure all the signals of the closedloop system were globally uniformly bounded. Simulation results showed the effectiveness of the proposed control algorithm.

    Preparation of nano-hydroxyapatite with the aid of ultrasonic waves
    ZHANG Ai-juan, LI Cheng-feng
    Abstract ( 273 )   PDF (1046KB) ( 1538 )   Save
    Related Articles | Metrics

    To solve the reunion problem of nano hydroxyapatite(HA) powders, the HA was prepared with the aid of ultrasonic wave and heated in 900℃, using Ca(NO3)2·4H2O and(NH4)2HPO4 as raw materials.The phase composition, chemical composition, micromorphology, thermal stability of the obtained HA were respectively studied by XRD, SEM, FTIR and TG-DTA. The results indicated that the micromorphology of synthesized HA with a mean size of 50nm was an isometric crystal and its uniformity and dispersity was good. The ultrasonic wave treatment of nano-scale powders could solve the reunion problem to a certain extent, and  heat-treatment could improve the crystallinity of HA grains.

    Enhanced light harvesting and photocatalytic property of TiO2 architecture derived from butterfly wings
    LIU Hui-hui, FAN Tong-xiang *
    Abstract ( 250 )   PDF (1165KB) ( 2066 )   Save
    Related Articles | Metrics

    Nature’s multi-porous architectures in micro and nano scale were proved to enhance light harvesting. In order to enhance the light harvesting efficiency of TiO2 and improve its photo catalytic property, TiO2 replicas with the wing scale architecture of the butterfly Papilio maackii were synthesized by a bio-template immerse  and  calcine method. The replicas inherited from the template both the inversed V shaped ridges and the nano pore arrays worked together and could enhance the light harvesting efficiency by making an ordered scattering and refraction pathway for the incident light. The photocatalytic properties of  wing architecture TiO2 replicas were tested, and the results showed an obvious improvement compared to normal TiO2 particles.

    Preparation of straight and orderly polypyrrole microrods through soft template methods
    LIU Feng, SHI Yuan-chang*, ZHANG Bing-chang, SUN Li-bo
    Abstract ( 292 )   PDF (1200KB) ( 2087 )   Save
    Related Articles | Metrics

    The straight and orderly microrods of polypyrrole(Ppy) were synthesized in a microemulsion system that  consisted of cetyltrimethylammonium bromide (CTAB), n-pentanol, water and pyrrole by chemical oxidative polymerization, in which CTAB was used as soft templates and ammonium persulfate (APS) were  used as the oxidant. Fourier-transform infrared spectroscopy (FTIR) were used to characterize the structure of the Ppy microrods. Transmission electron microscopy (TEM) and high resolution transmission electron microscopy(HRTEM) was used to characterize the morphology of the samples. The effects of temperature, the addition method   of the oxidant, and the amount of cosurfactant n-pentanol to the morphology of Ppy microrods were discussed. The results showed that when the temperature was kept at room temperature (25℃), the droping time of APS was about 1.5h, the ratio of CTAB to n-pentanol was 0.6∶1.0, and the polymerization time was 24h, the straight and orderly polypyrrole microrods with a diameter about 300nm and a length up to 20μm were synthesized.

    Study of the preparation of ZnO nanotorch-array thin film via solution treatment and its gas sensitivity
    LIU Zhe, TIAN Shou-qin, WANG Bo, ZENG Da-wen*, XIE Chang-sheng
    Abstract ( 244 )   PDF (1373KB) ( 1993 )   Save
    Related Articles | Metrics

    By using the seeded growth method and solution treatment, a layer of torch-like ZnO nano-array thin film was obtained on the surface of gas sensor devices. Proceeding at low temperature, this method was both environment-friendly and energy-conserving. The thin film’s X-ray diffraction (XRD) pattern indicated that the components of the film were mainly derived from Wurtzite type ZnO. The structural information obtained with field-emission scanning electron microscopy (FESEM) showed the morphology of hollow ZnO nanotorches with a height of 5 μm, an outside diameter of 2 μm and thickness of 200 nm,  were generally even-sized as well as regularly arrayed. These ZnO nanotorches were mainly assembled by even finer ZnO particles with a diameter of around 20 nm. Also , a possible growth mechanism of the ZnO nanotorches was discussed. Finally, the gas sensitivity to ethanol of these  hollow ZnO nanotorches material was measured, and the result demonstrated that the ZnO nanotorches had better gas sensitivity  than those already known ZnO materials with morphologies such as nanorods and nanowalls.

    Study on milling stability of thin-walled titanium alloy components with paraffin reinforcement
    GE Mao-jie1,2, SUN Jie1,2*, LI Jian-feng1,2
    Abstract ( 207 )   PDF (2858KB) ( 1555 )   Save
    Related Articles | Metrics

    Aiming at the technical problems such as low stiffness, vibration and dimension error in milling thin-walled titanium alloy components, milling experiments with and without paraffin reinforcement were conducted. The acceleration signals in the milling process and the surface roughness of the finished part were measured and analyzed. It was shown that paraffin reinforcement can significantly improve  machining stability and  surface finish. The paraffin reinforcement mechanism in milling thin-walled titanium alloy component was also studied.

    Application research on CBR technology used in modular variant design
    DU Hui1,2, YE Wen-hua1, LOU Pei-huang1
    Abstract ( 278 )   PDF (2155KB) ( 1087 )   Save
    Related Articles | Metrics

    In order to improve the efficiency of modular variant design, a method of case-based reasoning combined with modular variant design(CBRMD)was put forward. Case-based reasoning(CBR)technology was used in modular variant design,  similar case of product and structure module was retrieved by CBR, self-organizing maps (SOM) networks were employed to cluster past cases, and then the layered case base was  constructed with clustered cases. Finally, through the example of modular design of machine center, the practical value of the proposed method was revealed.

    Research on the turning safety of heavy vehicles
    CHEN Hui, LI Xiang-hua, DENG Hua*
    Abstract ( 314 )   PDF (842KB) ( 1260 )   Save
    Related Articles | Metrics

    In order to analyze effectively the turning safety of heavy vehicles, the dynamic model and lateral balance equations of the whole vehicle were established by using the Lagrange method. The allowance of sideslip and rollover were defined, and the sequences of rollover and sideslip were determined.Based on the above analysis, the influence of the factors such as cross road adhesion coefficient to the lateral stability were analyzed, Moreover, the influence of roll-yaw inertia on the stability was further investigated. Finally, the turning characteristics of a heavy vehicle were simulated. It was found that the sideslip is mainly affected by the cross road adhesion coefficient, the rollover is mainly affected by the ratio between mass-center height and vehicle width,  and the stability of the model is  affected by the product of inertia.

    Assessment of cerebral oxygenation response to vibration in drivers
    ZHANG Liang-liang1,2, LI Jian-ping1,2, WANG Yan1,2, CHEN Guo-qiang1,2, LI Zeng-yong1,2*
    Abstract ( 286 )   PDF (1517KB) ( 1583 )   Save
    Related Articles | Metrics

    The effects of vibration on oxygenation response were  assessed. The cerebral blood parameters were monitored and recorded using  near infrared spectroscopy during the experiment. Based on variance analysis, remarkable variations of the parameters in the cerebral tissue blood were found(P<0.01). The result of the experiment demonstrated that concentration of hemoglobin(cHb),oxyhemoglobin(cHbO2) and the sum of hemoglobin(ctHb) are significantly influenced by vehicle vibration.Furthermore, the influence of different frequencies is significantly different, the influence of 4.5Hz vibration is the most remarkable. Whereas, the tissue oxygen index (TOI) is little influenced by all the vehicle vibration of the three frequencies.

    Influencing factors analysis of residual deformation of doubly symmetric stainless steel flexural members
    WANG Yuan-qing1, GAO Bo2*, DAI Guo-xin2, SHI Yong-jiu1, YUAN Huan-xin1
    Abstract ( 409 )   PDF (1902KB) ( 1430 )   Save
    Related Articles | Metrics

    In order to investigate residual deformation and  strength of doubly symmetric stainless steel flexural members,  influencing factors analysis was presented by adopting the residual displacement method suggested by Mazzolani. With  finiteelement analysis (FEA), 340 stainless steel I-beams were computed and the plastic adaption coefficient was suggested, which controlled the residual displacement less than 1/1000 of the beam span. The relationship between the plastic adaption coefficient and the geometry of members and material property was deduced. Design methods based on the FEA results were also proposed. The results indicated that the plastic adaption coefficient is the best way to control the residual deformation and ensure the requirements of the strength and deformation of stainless steel flexural members.

    The application of TEM geological forecast about the F1-2 water-bearing  fault of the Kiaochow Bay subsea tunnel
    LI Zhi-peng, ZHANG Qing-song*, LI Shu-cai, XUE Yi-guo, SU Mao-xin, DING Zhi-hai, ZHANG Wei-jie
    Abstract ( 356 )   PDF (1294KB) ( 1225 )   Save
    Related Articles | Metrics

    Transient electromagnetic method is an effective way to predict the water for its sensitivity to the low resistance body, so it was  used  to detect the F1-2 water-bearing fault of the Kiaochow Bay subsea tunnel. The results were analyzed after excluding interfering factors in the signal acquisition and data processing. Finally the scale and location of theF1-2  waterbearing fault、and degree of rock weathering、growth of water-bearing fault fissure water were determined, these parameters provide  effective geological information for the advance pre-grouting reinforcement. The advance exploration hole and geological record of this section proved the accuracy and effectiveness of this prediction, which will also be  a very good reference and guide for  succeeding tunnel geological predictios.

    Study on crystallization kinetics of glyphosate
    ZENG Xiang-dong, SHA Zuo-liang*, CHEN Qi-hua
    Abstract ( 407 )   PDF (854KB) ( 1569 )   Save
    Related Articles | Metrics

    The study of  crystallization kinetics could provide  the basic data for crystallizer design, scale-up, optimization and control of the crystallization process. The solubility of glyphosate in its synthesis mother liquor was  experimentally measured. The crystallization kinetics of glyphosate in its synthesis mother liquor was also experimentally measured in a mixed suspension mixed product removal (MSMPR) crystallizer. The size-independent crystal growth rate model  determined by the linear extrapolation population density distribution, the size-dependent crystal growth rate model, and the  nucleation rate model  determined by  the extrapolated population density distribution to the zero-size crystals were obtained. The experimental results showed that the solubility of glyphosate increased with the temperature increasing, which could make  cooling crystallization  possible for crystallizing glyphosate. The glyphosate crystal growth rate was size-dependent, and the suspension density and energy input had little effect on nucleation rate under experimental conditions.

    Hydrothermal synthesis and characterization of monodispersed ZnS microspheres
    GONG Xu-chun1, LIU Bao1*, YU Li-li1, DOU Zhen-wei2
    Abstract ( 387 )   PDF (974KB) ( 1723 )   Save
    Related Articles | Metrics

    Monodispersed ZnS microspheres were hydrothermally synthesized under low temperature using zinc acetate and sodium thiosulfate as raw materials, and cetyltrimethyl ammonium bromide (CTAB) as surfactant. The particles were characterized by XRD, TEM, SEM and FT-IR. The results showed that the smooth particles were of cubic phase, well-dispersed and had uniform size of 3 μm in diameter, and the characteristic absorption peaks of Zn—S appeared in the FT-IR spectra. Also, the possible growth mechanism was discussed.

    Influence of pH value in a phosphating bath on  zinc phosphate coatings on the AZ61 magnesium alloy
    ZHOU Ting-ting1, DU Ai-ling1*, GAO Yu1, YANG Yan-ling2
    Abstract ( 294 )   PDF (1719KB) ( 1216 )   Save
    Related Articles | Metrics

    The properties and microstructure of the zinc phosphate coatings on the AZ61D magnesium alloy prepared in phosphating baths with different pH values were studied. Weight loss test, anodic polarization measurement and electrochemical impedance spectroscopy were used to access the corrosion resistance of phosphate coatings. The structure and surface morphologies of phosphate coatings were observed by a metallographical microscope and analytical electron microscope. Results indicated that the pH values of phosphating baths had obvious effect on the anticorrosive performance and surface morphologies of phosphate coatings on the magnesium alloy. Phosphate coatings obtained in the baths with higher pH values were porous  with poor anticorrosive performance, while the coatings fabricated at lower pH values were coarse  with poor anticorrosive performance.The coatings prepared at a moderate pH value (pH value was 2.5) were uniform and with good anticorrosive performance.

    Experimental studies on  air-foam flooding in a heterogeneous reservoir at late high water cut stage
    CHEN Hui
    Abstract ( 258 )   PDF (1926KB) ( 1158 )   Save
    Related Articles | Metrics

    After  oil recovery in Gudao Oil Field by water flooding, polymer flooding and subsequent water flooding, the remaining  underground oil is highly decentralized, the watercut of the producing fluid is higher, and the producing process becomes more difficult. How to enhance oil recovery of the subsequent water flooding reservoir is especially important, which can improve the overall development performance of the oil field. With the principle of profile control and oil drive,  indoor research on enhancing recovery about airfoam flooding was put forth. A lab test simulated the geological model of a positive rhythmic reservoir at high water cut stage,which was composed of  high/middle/low permeability parallel core. By determining the resistance factor with different mass fractions of blowing agent and different gas/liquid ratios, the best optimized results were obtained. The best mass fraction of blowing agent was 0.5%, and the best underground gas/liquid volume ratio was 1∶1. Indoor laboratory investigation was  carried out concerning seal, profile and oil displacement characteristics under the conditions of low and high ratios of total oil produced to the original oil in place. The results showed that on the condition of low recovery percent after water drive (15.37%), and the enhanced oil recovery (EOR) increased 22.02% by air foam flooding. After the first round air foam flooding and succeeding water flooding, the EOR was  increased 9.35% by the second air foam flooding with pure air slug, and with a  recovery percent of 45.53%.

    Hofmann degradation of poly(AM/AMPS) in  inverse emulsion and its application in removal of the Cu(II) ion
    ZHANG Bao-liang1, WANG Hong-yun1, QIN Xu-ping1*, ZHAO Fang1, FENG Wei-hong1, GUO BO2
    Abstract ( 327 )   PDF (1203KB) ( 1081 )   Save
    Related Articles | Metrics

    An amphoteric poly(acrylamide/2-acrlamido-2-methylpropane sulphonic acid/vinylamine)(poly(AM/AMPS/VAm)) with strong absorbability of copper(II) ions was prepared by Hofmann degradation. First, the poly(AM/AMPS) was synthesized by inverse emusion polymerzation using AM and AMPS as monomers. Second, the partial  amide groups of the poly(AM/AMPS) were transformed to amine groups by the Hofmann degradation in the inverse emusion to obtain amphoteric poly(AM/AMPS/VAm). The effects of copolymerization and Hofmann degradation on their properties were discussed. The amine groups were confirmed using a FT-IR spectroscopy, and their amination value was calculated by the conductivity method. The influencing factors of removing the copper(II) ions in the simulated environment of the wastewater were investigated, such as reaction time, reaction temperature, pH value,  concentration of the copper(II) ions and the amount of products. The products before and after absorbed Cu2+ were characterized by SEM. The results indicated that the amphoteric poly(AM/AMPS/VAm) were of significant utility to remove the copper(II) ions.

    Kinetics of the adsorption of Reactive Brilliant Red K-2BP onto    modified wheat residue
    ZHONG Qian-qian, YUE Qin-yan*, LI Qian, LI Ying, XU Xing, GAO Bao-yu
    Abstract ( 319 )   PDF (1625KB) ( 2842 )   Save
    Related Articles | Metrics

    For removing the dye from wastewater, the wheat residue was modified into an anion exchanger. The adsorption kinetics of Reactive Brilliant Red K-2BP (RBR K-2BP) from aqueous solutions onto modified wheat residue(MWR)were  studied in a batch reactor. Adsorption experiments were carried out as a function of pH and adsorbent dosage. In addition, the kinetic data were respectively fitted by pseudo-first-order equation, pseudo-second-order equation, Elovich equation and the intraparticle diffusion model. It was found that the pseudo-second-order equation could  provide  the best correlation to the data. The intra-particle diffusion was the main rate-controlling step for the adsorption of RBR K-2BP onto MWR. The adsorption activation energy of dye was 17.21kJ/mol, which indicated that the adsorption type  whole process was mainly of the physical adsorption.

    Effects of Na-montmorillonite particles on emulsification stability of polymer flooding produced water
    LU Feng-juan1, LI Yu-jiang1*, SUN De-jun2, WU Tao2
    Abstract ( 276 )   PDF (1111KB) ( 1253 )   Save
    Related Articles | Metrics

    The effects of Namontmorillonite(Na-Mt)particles on the oil-water interfacial properties and oil-water separation of polymer flooding produced water were experimentally investigated. By using an interfacial rheometer and Zeta potentiometer to analyze the influences of Na-Mt particles on Zeta potential, interfacial tension and dilational viscoelasticity of polymer flooding produced water, and the adsorption of the Na-Mt particles on oil droplets was observed under optical microscopy. The result showed that with the Na-Mt particles concentration increasing, and when the Na-Mt particle concentration was less than 200mg/L, the Na-Mt particles could cause the Zeta potential of oil droplets to rapidly decrease, interfacial tension to decline and dilational viscoelasticity to be enhanced. The results also showed that a stable oil-mineral aggregate(OMA) structure appeared in polymer flooding produced water, which had noticeable effects on emulsification stability of polymer flooding produced water. The polymer flooding produced water was stable in this stage. When Na-Mt particle concentration was higher than 250mg/L, the Zeta potential of oil droplets keeps stable, while interfacial tension and dilational viscoelasticity showed a slight increase. The system formed a large oil-mineral aggregate structure, which was  apt to aggregate, and could enhance the treatment of polymer flooding produced water.

    Influence of porous medium on convective heat and mass transfer in a partially porous cavity
    LIU Fang1,2, CHEN Bao-ming2, WANG Li2
    Abstract ( 299 )   PDF (2568KB) ( 1214 )   Save
    Related Articles | Metrics

    Natural convective heat and mass transfer in a partially filled with porous medium was studied by using the two-domain approach. The Forheimer-Brinkman-Darcy equation was developed for the porous medium, whereas the Navier-Stokes equation was set up for the clear fluid region. A continuous interfacial condition was used at the interface between the clear fluid region and porous medium and the equations were solved by the finite element method with  weak constraint condition at the interface. Influences of thickness, permeability and porosity of the porous medium on heat and mass transfer were mainly considered. The numerical results showed that heat and mass transfer could be quickly weakened  when thickness of the porous medium is no more than 0.2. The flow became obviously slower when permeability decreased from 10-3   to 10-6 and also heat and mass transfer. Average heat and mass transfer velocities increased linearly with an increasing porosity.

    System design of magnetic bearings in an axial-flow artificial blood pump
    GUAN Yong, LI Hong-wei, LIU Shu-qin*
    Abstract ( 347 )   PDF (1217KB) ( 1946 )   Save
    Related Articles | Metrics

    The artificial blood pump has to meet the following advantages, small volume and mass and low power consumption. Radial permanent magnetic bearings (RPMBs) and axial electromagnetic bearings (AEMBs) were employed in the magnetic levitated artificial blood pump to suspend the rotor in five degree of freedoms (DOFs) and to meet the above requirements. According to the mechanical equilibrium condition of the blood pump rotor, two structure design methods were presented for the magnetic levitated system of the blood pump. One can be called the low power consumption design method and the other can be called the single axial EMB design method. The design principals of radial PMB and axial EMB in the two methods were given. Compared with the first method, the second method  simplifies the blood pump structure and the axial EMB’s controller, and greatly reduces the pump volume and mass, though it maybe require more power consumption. A prototype axialflow magnetic levitated blood pump was designed and manufactured according to the second method.  Experimental results showed that the rotor was successfully and stably suspended in five DOFs by radial PMBs and only one axial EMB. These results showed that the magnetic bearing system structure design method presented is feasible. This study will provide references to the structure design of the magnetic levitated artificial blood pump.

    Intermittent heat emission study of the temperature environment of an air source heat pump using air in an underground tunnel
    LI Yi, TIAN Mao-cheng, LI Yong-an
    Abstract ( 311 )   PDF (1861KB) ( 1371 )   Save
    Related Articles | Metrics

    The research analyzed the feasibility of using air in an underground tunnel as cold and heat sources of heat pumps, modeled building of tunnel heat transfer, obtained  internal  and external boundary conditions, then simplified and solved it with Laplace mathematics transform, and obtained  the heat exchange formula of air passing through a tunnel. Then modeled physical building of the temperature environment and obtained boundary conditions, and used FLUENT software to numerically simulate with dynamic boundary conditions, then obtained  the results and compared then with  experimental  data, and finally found dynamic heat transfer characteristics and some key problems of using air in an underground tunnel as cold and heat sources of heat pumps. It can provide some practical help on tunnel wind cooling technology and heat transfer, simulate calculating of using air in underground tunnel as cold and heat sources of heat pumps, and also on  saving energy consumption and environmental protection research.

    Simulating the effects of an intake resonator on volumetric efficiency of a gasoline engine
    MA Zong-zheng, CHENG Yong*
    Abstract ( 453 )   PDF (2508KB) ( 2672 )   Save
    Related Articles | Metrics

    The intake resonator system is one of the useful ways to improve the power performance of the engine. Based on the validation of the simulation model, the effects of the resonator parameters, such as resonant volume, resonator pipe length and diameter, on the volumetric efficiency were studied by the BOOST simulation code. The results showed that with the resonator the volumetric efficiency increased by 2% around the resonance speed. The maximum volumetric efficiency point could be changed by modifying the resonance volume, resonance pipe diameter or length, and the speed corresponding to maximum volumetric efficiency was 50r/min higher than the resonance speed. The volumetric efficiency of the engine could be improved if the cross sectional area of the resonance pipe was close to the effective charging area. Too large a resonance volume or too long a resonance pipe could reduce the effect of the resonator.

    A dynamic multi-objective optimization evolutionary algorithm based on estimation of core distribution
    LIU Chun-an
    Abstract ( 235 )   PDF (918KB) ( 1646 )   Save
    Related Articles | Metrics

    An estimation of core distribution method to approximately estimate the evolution population and the Pareto optimization solution set for the problem in the next environment was given. When a change in the environment was detected, the algorithm used the collected information of solutions from the previous difficult environments to predict the evolution population and the Pareto optimization solution set in the next environment. Consequently, the searching effectiveness of the proposed algorithm can be greatly improved. By the reasonable designing of evolution operators, a new dynamic multiobjective optimization evolutionary algorithm based on estimation of core distribution was proposed. Simulations were made on four widely used benchmark problems, and the results indicated that the proposed algorithm was very effective.